The Carbonia Oil used in the American Gas Furnace 'Carbonia Bluing' was a proprietary mix. A very heavy weight oil (molasses heavy), but of simple substances of the period.
IIRC the main ingredients were a locomotive cylinder lube and a specific species pine tar. The ratio I don't recall.

It had a lot to do with the color produced by the system which was an early automated of sorts method of the more labor intensive charcoal bluing. The latter produces a very similar but not quite the same look.

Different oil(s) can be used in the Amer Gas Furnace system for bluing, even common linseed oil.
Even Winchester used linseed in their AGFurnace bluing of small parts like pins, screws, washers, ect.
The blue is not quite the same color, but the cost was much less than buying AGF propietary oil for that. Most wouldn't notice the difference I don't think on smaller parts.

The system was used by other industries too like the hardware industry. Remember when nuts, bolts and screws and washers were all blued,,those were done in huge quantities by some companys in the same system,,and with cheap easily gotten common oil for the primer.

When I worked for a major restoration shop and we were trying to develop a gas furnace type bluing, we asked Mobil (they had a nearby research lab) about the Carbonia oil. We found they knew about it, but had no souce for it.
They did send a large bucket of some sort of synthetic black goop over to try,,it was a Mobil product, not some mixed up one-of. They said it was the 'same as' carbonia oil as far as lube specs go.
It worked,,kind of, like so many other oils will work,but didn't give that proper color and tone for the critical look of a restoration.
I don't know what they're using now.
Most are satisfied with shiny & blue. That's a long way from a restoration that begins with a proper polish anyway.